One of the key themes of Stack Exchange right from the start has been that you can't have a site about everything. Each SE site has a topic, users who are devoted to that topic, and who will ruthlessly exclude questions that aren't on that topic. This can be a bit confusing at times, especially to new users, but the value of a focused community that knows its specialty and works to emphasize it outweighs this...
In the League of Justice, each hero combines forces to make something greater than the whole — without sacrificing their original identity. The power of the League is self-evident and testament to the individual strength of each member.
Skeptics is a bit of an odd duck in this, since its topic isn't quite as obvious as, say, Cooking or Gardening. This site isn't about medicine, or history, or nutrition, although questions on all of those topics can be on-topic... It's not even about Skepticism!
Skeptics is about applying skepticism — it's for researching the evidence behind the claims you hear or read. It is not for philosophical discussions about skepticism itself.
That said, it does have a topic, a set of questions that are on-topic and a much larger set that aren't - just like every other SE site. The key is in that first paragraph from the FAQ I just quoted: it's about claims heard or read.
It's tempting to let this scope just keep expanding until it does cover everything... Now, I don't pretend to know every claim ever said or written. But I've spent a lot of time engaged in idle speculation, and I know what that looks like:
This is dangerous. With no burden of proof on the asker that someone else believes the claim they're asking you to fact-check, you risk losing your specialty... And eventually, your experts. D'ya think Superman would keep showing up for the League of Justice if folks were bugging him every time they needed furniture moved or a jar opened?
Now, that doesn't mean every single claim has to be backed by a New York Times article making it. You could probably even let "It's commonly said..." claims slide, if the claim is actually common knowledge. But if there's any doubt - if one person shows up, searches for evidence that the claim is notable, and then disputes the claim (leaves a comment, or flags for moderator attention) - then it's the responsibility of the asker (or your friendly neighborhood editor) to dig up a real, verifiable source. After all, if it's actually common knowledge, then there should be some reference to it out there...
Please, don't let this site become SE Answers, the dumping ground for idle curiosity and pointless speculation. Don't cripple your superhero: cite, flag, or close, and let your experts focus on real claims.